Lung volume reduction therapy using crosslinked non-natural polymers

ABSTRACT

One aspect of the invention relates to a hydrogel comprising a non-natural polymer comprising a plurality of pendant nucleophilic groups and a crosslinker comprising at least two pendant electrophilic groups. Another aspect of the invention relates to a hydrogel comprising a non-natural polymer comprising a plurality of pendant electrophilic groups and a crosslinker comprising at least two pendant nucleophilic groups. Yet another aspect of the invention relates to a method for reducing lung volume in a patient comprising the step of administering a hydrogel composition as described herein. Further, hydrogels of the invention may be used to achieve pleurodesis, seal brochopleural fistulas, seal an air leak in a lung, achieve hemostasis, tissue sealing (e.g., blood vessels, internal organs), or any combination thereof. In certain embodiments, the compositions and methods described herein are intended for use in the treatment of patients with emphysema.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/117,367, filed May 8, 2008, which claims the benefit of U.S.Provisional No. 60/917,419, filed May 11, 2007. These applications areincorporated herein by reference in their entirety.

BACKGROUND

Emphysema is a common form of chronic obstructive pulmonary disease(COPD) that affects between 1.5 and 2 million Americans, and 3 to 4times that number of patients worldwide. [American Thoracic SocietyConsensus Committee “Standards for the diagnosis and care of patientswith chronic obstructive pulmonary disease,” Am. J. Resp. Crit. CareMed. 1995, 152, 78-83; and Pauwels, R., et al. “Global strategy for thediagnosis, management, and prevention of chronic obstructive pulmonarydisease,” Am. J. Resp. Crit. Care Med. 2001, 163, 1256-1271.] It ischaracterized by destruction of the small airways and lung parenchymadue to the release of enzymes from inflammatory cells in response toinhaled toxins. [Stockley, R. “Neutrophils and protease/antiproteaseimbalance,” Am. J. Resp. Crit. Care Med. 1999, 160, S49-S52.] Althoughthis inflammatory process is usually initiated by cigarette smoking,once emphysema reaches an advanced stage, it tends to progress in anunrelenting fashion, even in the absence of continued smoking [Rutgers,S. R., et al. “Ongoing airway inflammation inpatients with COPD who donot currently smoke,” Thorax 2000, 55, 12-18.]

The class of enzymes that are responsible for producing tissue damage inemphysema are known as proteases. These enzymes are synthesized byinflammatory cells within the body and when released, they act todegrade the collagen and elastin fibers which provide mechanicalintegrity and elasticity to the lung. [Jeffery, P. “Structural andinflammatory changes in COPD: a comparison with asthma,” Thorax 1998,53, 129-136.] The structural changes that result from the action ofthese enzymes are irreversible, cumulative, and are associated with lossof lung function that eventually leaves patients with limitedrespiratory reserve and reduced functional capacity. [Spencer, S. et al.“Health status deterioration inpatients with chronic obstructivepulmonary disease,” Am. J. Resp. Crit. Care Med. 2001, 163, 122-128; andMoy, M. L., et al. “Health-related quality of life improves followingpulmonary rehabilitation and lung volume reduction surgery,” Chest 1999,115, 383-389.]

In contrast to other common forms of COPD, such as asthma and chronicbronchitis for which effective medical treatments exist, conventionalmedical treatment is of limited value in patients with emphysema.Although emphysema, asthma, and chronic bronchitis each cause chronicairflow obstruction, limit exercise capacity, and cause shortness ofbreath, the site and nature of the abnormalities in asthma and chronicbronchitis are fundamentally different from those of emphysema. Inasthma and chronic bronchitis, airflow limitation is caused by airwaynarrowing due to smooth muscle constriction and mucus hyper-secretion.Pharmacologic agents that relax airway smooth muscle and loosenaccumulated secretions are effective at improving breathing function andrelieving symptoms. Agents that act in this way include beta-agonist andanti-cholinergic inhalers, oral theophylline preparations, leukotrieneantagonists, steroids, and mucolytic drugs.

In contrast, airflow limitation in emphysema is not primarily due toairway narrowing or obstruction, but due to loss of elastic recoilpressure as a consequence of tissue destruction. Loss of recoil pressurecompromises the ability to fully exhale, and leads to hyper-inflationand gas trapping. Although bronchodilators, anti-inflammatory agents,and mucolytic agents are frequently prescribed for patients withemphysema, they are generally of limited utility since they are intendedprimarily for obstruction caused by airway disease; these classes ofcompounds do nothing to address the loss of elastic recoil that isprincipally responsible for airflow limitation in emphysema. [Barnes, P.“Chronic Obstructive Pulmonary Disease,” N. Engl. J. Med. 2000, 343(4),269-280.]

While pharmacologic treatments for advanced emphysema have beendisappointing, a non-medical treatment of emphysema has recentlyemerged, which has demonstrated clinical efficacy. This treatment islung volume reduction surgery (LVRS). [Flaherty, K. R. and F J. Martinez“Lung volume reduction surgery for emphysema,” Clin. Chest Med. 2000,21(4), 819-48.]

LVRS was originally proposed in the late 1950s by Dr. Otto Brantigan asa surgical remedy for emphysema. The concept arose from clinicalobservations which suggested that in emphysema the lung was “too large”for the rigid chest cavity, and that resection of lung tissuerepresented the best method of treatment since it would reduce lungsize, allowing it to fit and function better within the chest. Initialexperiences with LVRS confirmed that many patients benefitedsymptomatically and functionally from the procedure. Unfortunately,failure to provide objective outcome measures of improvement, coupledwith a 16% operative mortality, led to the initial abandonment of LVRS.

LVRS was accepted for general clinical application in 1994 through theefforts of Dr. Joel Cooper, who applied more stringent pre-operativeevaluation criteria and modern post-operative management schemes toemphysema patients. [Cooper, J. D., et al. “Bilateral pneumonectomy forchornic obstructive pulmonary disease,” J. Thorac. Cardiovasc. Surg.1995, 109, 106-119.] Cooper reported dramatic improvements in lungfunction and exercise capacity in a cohort of 20 patients with advancedemphysema who had undergone LVRS. There were no deaths at 90-dayfollow-up, and physiological and functional improvements were markedlybetter than had been achieved with medical therapy alone.

While less dramatic benefits have been reported by most other centers,LVRS has nevertheless proven to be effective for improving respiratoryfunction and exercise capacity, relieving disabling symptoms of dyspnea,and improving quality of life in patients with advanced emphysema.[Gelb, A. F., et al. “Mechanism of short-term improvement in lungfunction after emphysema resection,” Am. J. Respir. Crit. Care Med.1996, 154, 945-51; Gelb, A. F., et al. “Serial lung function and elasticrecoil 2 years after lung volume reduction surgery for emphysema,” Chest1998, 113(6), 1497-506; Criner, G. and G. E. D'Alonzo, Jr., “Lung volumereduction surgery: finding its role in the treatment of patients withsevere COPD,” J. Am. Osteopath. Assoc. 1998, 98(7), 371; Brenner, M., etal. “Lung volume reduction surgery for emphysema,” Chest 1996, 110(1),205-18; and Ingenito, E. P., et al. “Relationship between preoperativeinspiratory lung resistance and the outcome of lung-volume-reductionsurgery for emphysema,” N. Engl. J. Med. 1998, 338, 1181-1185.] Thebenefits of volume reduction have been confirmed in numerous cohortstudies, several recently-completed small randomized clinical trials,and the National Emphysema Treatment Trial (NETT). [Goodnight-White, S.,et al. “Prospective randomized controlled trial comparing bilateralvolume reduction surgery to medical therapy alone inpatients with severeemphysema,” Chest 2000, 118(Suppl 4), 1028; Geddes, D., et al.“L-effects of lung volume reduction surgery inpatients with emphysema,”N. Eng. J. Med. 2000, 343, 239-245; Pompeo, E., et al. “Reductionpneumoplasty versus respiratory rehabilitation in severe emphysema: arandomized study,” Ann. Thorac. Surg. 2000, 2000(70), 948-954; andFishman, A., et al. “A randomized trial comparing lung-volume-reductionsurgery with medical therapy for severe emphysema,” N. Eng. J. Med.2003, 348(21): 2059-73.] On average, 75-80% of patients have experienceda beneficial clinical response to LVRS (generally defined as a 12% orgreater improvement in FEV, at 3 month follow-up). The peak responsesgenerally occur at between 3 and 6 months post-operatively, andimprovement has lasted several years. [Cooper, J. D. and S. S. Lefrak“Lung-reduction surgery: 5 years on,” Lancet 1999, 353(Suppl 1), 26-27;and Gelb, A. F., et al. “Lung function 4 years after lung volumereduction surgery for emphysema,” Chest 1999, 116(6), 1608-15.] Resultsfrom NETT have further shown that in a subset of patients withemphysema, specifically those with upper lobe disease and reducedexercise capacity, mortality at 29 months is reduced.

Collectively, these data indicate that LVRS improves quality of life andexercise capacity in many patients, and reduces mortality in a smallerfraction of patients, with advanced emphysema. Unfortunately, NETT alsodemonstrated that the procedure is very expensive when considered interms of Quality Adjusted Life Year outcomes, and confirmed that LVRS isassociated with a 5-6% 90 day mortality. [Chatila, W., S. Furukawa, andG. J. Criner, “Acute respiratory failure after lung volume reductionsurgery,” Am. J. Respir. Crit. Care Med. 2000, 162, 1292-6; Cordova, F.C. and G. J. Criner, “Surgery for chronic obstructive pulmonary disease:the place for lung volume reduction and transplantation,” Curr. Opin.Pulm. Med. 2001, 7(2), 93-104; Swanson, S. J., et al. “No-cutthoracoscopic lung placation: a new technique for lung volume reductionsurgery,” J. Am. Coll. Surg. 1997, 185(1), 25-32; Sema, D. L., et al.“Survival after unilateral versus bilateral lung volume reductionsurgery for emphysema,” J. Thorac. Cardiovasc. Surg. 1999, 118(6),1101-9; and Fishman, A., et al. “A randomized trial comparinglung-volume-reduction surgery with medical therapy for severeemphysema,” N. Engl. J. Med. 2003, 348(21), 2059-73.] In addition,morbidity following LVRS is common (40-50%) and includes a highincidence of prolonged post-operative air-leaks, respiratory failure,pneumonia, cardiac arrhythmias, and gastrointestinal complications. Lessinvasive and less expensive alternatives that could produce the samephysiological effect are desirable.

A hydrogel-based system for achieving lung volume reduction has beendeveloped and tested, and its effectiveness confirmed in both healthysheep, and sheep with experimental emphysema. [Ingenito, E. P., et al.“Bronchoscopic Lung Volume Reduction Using Tissue EngineeringPrinciples,” Am. J. Respir. Crit. Care Med. 2003, 167, 771-778.] Thissystem uses a rapidly-polymerizing, fibrin-based hydrogel that can bedelivered through a dual lumen catheter into the lung using abronchoscope. The fibrin-based system effectively blocks collateralventilation, inhibits surfactant function to promote collapse, andinitiates a remodeling process that proceeds over a 4-6 week period.Treatment results in consistent, effective lung volume reduction. Thesestudies have confirmed the safety and effectiveness of usingfibrin-based hydrogels in the lung to achieve volume reduction therapy.

While the above-mentioned studies confirmed the efficacy of afibrin-based system for lung volume reduction, the system is complex,comprising more than 5 different components, and fibrinogen and thrombinare blood-derived. Further, the potential patient population is so largethat wide-spread use could consume all of the fibrinogen producedworldwide. Moreover, because the product is derived from blood,contamination with blood-borne pathogens is always a concern. Lastly,fibrinogen-based systems are expensive. Accordingly, there is a need todevelop a less-expensive system for lung volume reduction based onsynthetic polymers.

SUMMARY

One aspect of the invention relates to a hydrogel comprising anon-natural polymer comprising a plurality of pendant nucleophilicgroups and a crosslinker comprising at least two pendant electrophilicgroups. Another aspect of the invention relates to a hydrogel comprisinga non-natural polymer comprising a plurality of pendant electrophilicgroups and a crosslinker comprising at least two pendant nucleophilicgroups.

One aspect of the invention relates to a hydrogel comprising anon-natural polymer comprising a plurality of pendant primary aminegroups and a crosslinker. In certain embodiments the invention relatesto a three-dimensional matrix of a hydrogel formed by chemically linkingnon-natural polymer chains with pendant primary amines using apolyaldehyde. In certain embodiments, the hydrogel composition is mixedwith a gas to form a foam.

One aspect of the invention relates to a hydrogel comprising anon-natural polymer comprising a plurality of pendant primary aminegroups (which have been formed from pendant hydroxyl groups by reactionwith an amine-containing compound) and a crosslinker. In certainembodiments the invention relates to a three-dimensional matrix of ahydrogel formed by chemically linking non-natural polymer chains withpendant primary amines using a polyaldehyde. In certain embodiments, thehydrogel composition is mixed with a gas to form a foam.

Another aspect of the invention relates to a method for reducing lungvolume in a patient comprising the step of administering a hydrogelcomposition as described herein. In certain embodiments, the hydrogelcomposition comprises a first amount of a non-natural polymer containinga plurality of pendant primary amines and a second amount of acrosslinker, thereby forming a hydrogel in said region. In certainembodiments, the crosslinker is a dialdehyde. In certain embodiments,the crosslinker is glutaraldehyde. In certain embodiment, said hydrogelcomposition further comprises a gas. In certain embodiments, said gas isair or oxygen.

Another aspect of the invention relates to a method for reducing lungvolume in a patient comprising the step of administering a hydrogelcomposition as described herein. In certain embodiments, the hydrogelcomposition comprises a first amount of a non-natural polymer containinga plurality of pendant primary amines, wherein said non-natural polymercontaining a plurality of pendant primary amines is derived from anon-natural polymer containing a plurality of pendant hydroxyl groups,and a second amount of a crosslinker, thereby forming a hydrogel in saidregion. In certain embodiments, the polymer containing a plurality ofpendant hydroxyl groups is polyvinyl alcohol. In certain embodiments,the crosslinker is a dialdehyde. In certain embodiments, the crosslinkeris glutaraldehyde. In certain embodiment, said hydrogel compositionfurther comprises a gas. In certain embodiments, said gas is air oroxygen.

It should be appreciated that compositions of the invention also mayinclude one or more additional compounds (e.g., therapeutic compound(s),stabilizing compound(s), antibiotic(s), growth factor(s), etc.),buffers, salts, surfactants, anti-surfactants, lipids, excipients,and/or other suitable compounds. In certain embodiments, compositions ofthe invention may be sterilized.

In certain embodiments, compositions of the invention may be used toachieve pleurodesis, seal brochopleural fistulas, seal an air leak in alung, achieve hemostasis, tissue sealing (e.g., blood vessels, internalorgans), or any combination thereof. In certain embodiments, thecompositions and methods described herein are intended for use in thetreatment of patients with emphysema.

In certain embodiments, the compositions and methods cause minimaltoxicity, are injectable through a catheter, and polymerize rapidlyenough to prevent solution from spilling back into the airways followinginjection. Additional advantages and novel features of the presentinvention will become apparent from the following detailed descriptionof various non-limiting embodiments of the invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a reaction of polyvinyl alcohol (PVA) with an aminatingagent (e.g., electrophile tethered to a primary amine) to form anaminated PVA (aPVA); reaction of the aminated PVA with a cross-linkingagent (e.g., a dialdehyde); and cross-linking of the resulting productwith an aPVA.

FIG. 2 tabulates (Table 1) test articles; treatment groups (Table 2); CTscan findings (Table 3).

FIG. 3 depicts graphically the nitrogen content of various ABA-modifiedPVAs of the present invention. See Example Three.

FIG. 4 depicts graphically the time to solidification for mixtures of150 kDa ABA-PVA and GA as a function of percentage amination of theABA-PVA and the concentration of GA. See Example Four.

FIG. 5 depicts graphically the time to solidification for mixtures of100 kDa ABA-PVA and GA as a function of percentage amination of theABA-PVA and the concentration of GA. See Example Four.

FIG. 6 depicts graphically the time to solidification for mixtures of 4%150 kDa ABA-PVA and GA as a function of pH and the concentration of GA.See Example Four.

FIG. 7 depicts graphically the average normalized volume reduction pertreatment site from CT integration. Error bars represent one standarddeviation. See Example 5.

FIG. 8 depicts tabulated (Table 5) polymerization times foraPVA/Glutaraldehyde.

DETAILED DESCRIPTION

One aspect of the invention relates to compositions and methods fortreatment of patients with advanced emphysema. In certain embodiments,the invention relates to a system for achieving lung volume reductiontherapy, wherein an inventive composition is injected into the lung.

The composition serves several key functions that are beneficial forpromoting lung volume reduction: it blocks collateral ventilation bycoating the interstices of the lung surface, a step that prevents rapidre-inflation of the treatment area; it helps to ensure that reagentsremain localized to the treatment area, since upon polymerization, thecomposition becomes trapped in the small airways and alveoli of thelung, preventing flow beyond the intended treatment site; and it fillsthe treatment area, displacing air and forming a bridge between adjacentregions of lung tissue.

In certain embodiments, the composition is biodegradable or resorbable;therefore, the surrounding tissues may respond by degrading thecomposition and cells may start growing into the composition. Thebiological matrix deposited by these cells links the adjacent areas oftissue and may provide a permanent tissue bridge that ensures a durablevolume reduction response.

In certain embodiments, to be effective as a volume reducing agent inthe lung, the precursors of the composition must have sufficiently fastpolymerization kinetics and physical properties to allow for endoscopicdelivery. The compositions must show rapid polymerization, and havemechanical properties such that following polymerization the firmness ofthe composition does not mechanically injure adjacent soft lung tissues.Further, the compositions must have initial viscosities that will allowthem to be injected through a small-bore catheter. In addition, thecomposition must have acceptable pharmacokinetic degradation profiles invivo. The inventive compositions described herein which posses some orall of these features should be satisfactory for achieving bronchoscopiclung volume reduction therapy.

Herein are described compositions that possess some or all of theseproperties. In addition, in certain embodiments, the cross-linkedpolymer compositions of the invention may show superior properties tosome known LVRT compositions because of improved tissue adhesion; thecompositions of the invention may have minimal seepage and may beself-healing (i.e., substantially less cracks or breaks might be formedin the solidified mass).

There are many advantages to the compositions and methods describedherein. In some respects, the compositions described herein arechemically simpler than various current LVRT compositions. In certainembodiments, the chemicals are less expensive. In certain embodiments,the compositions of the invention have better space-fillingcharacteristics than fibrin-based hydrogel systems, meaning that smalleramounts of material may be used to collapse a given lung volume. Inaddition, in certain embodiments, there appears to be decreasedpotential for systemic toxicity than with some other LVRT approaches.

Generally, in order for a cross-linked polymer system to be useful forLVRT, the polymer system must have a number of qualities, including:

-   -   1. Polymerization time long enough to allow delivery to the lung        via a bronchoscopically placed catheter (approximately >1 min);    -   2. Fluid mechanical properties that allow injection through a        bronchoscopically-guided small bore catheter; and    -   3. Polymerization time short enough to allow practical procedure        length without spillage from the treatment site (approximately        <10 min).

DEFINITIONS

For convenience, certain terms employed in the specification andappended claims are collected here. These definitions should be read inlight of the entire disclosure and understood as by a person of skill inthe art.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

The term “biodegradable” is intended to mean any component capable ofdisappearing by progressive degradation (metabolism).

The term “contrast-enhancing” refers to materials capable of beingmonitored during injection into a mammalian subject by methods formonitoring and detecting such materials, for example by radiography orfluoroscopy. An example of a contrast-enhancing agent is a radiopaquematerial. Contrast-enhancing agents including radiopaque materials maybe either water soluble or water insoluble. Examples of water solubleradiopaque materials include metrizamide, iopamidol, iothalamate sodium,iodomide sodium, and meglumine. Examples of water insoluble radiopaquematerials include metals and metal oxides such as gold, titanium,silver, stainless steel, oxides thereof, aluminum oxide, zirconiumoxide, etc.

The term “alkyl” is art-recognized, and includes saturated aliphaticgroups, including straight-chain alkyl groups, branched-chain alkylgroups, cycloalkyl (alicyclic) groups, alkyl substituted cycloalkylgroups, and cycloalkyl substituted alkyl groups. In certain embodiments,a straight chain or branched chain alkyl has about 30 or fewer carbonatoms in its backbone (e.g., C₁-C₃₀ for straight chain, C₁-C₃₀ forbranched chain), and alternatively, about 20 or fewer. Likewise,cycloalkyls have from about 3 to about 10 carbon atoms in their ringstructure, and alternatively about 5, 6 or 7 carbons in the ringstructure.

Unless the number of carbons is otherwise specified, “lower alkyl”refers to an alkyl group, as defined above, but having from one to aboutten carbons, alternatively from one to about six carbon atoms in itsbackbone structure. Likewise, “lower alkenyl” and “lower alkynyl” havesimilar chain lengths.

The term “aralkyl” is art-recognized and refers to an alkyl groupsubstituted with an aryl group (e.g., an aromatic or heteroaromaticgroup).

The terms “amine” and “amino” are art-recognized and refer to bothunsubstituted and substituted amines.

The term “amido” is art recognized as an amino-substituted carbonyl.

The terms “alkoxyl” or “alkoxy” are art-recognized and refer to an alkylgroup, as defined above, having an oxygen radical attached thereto.Representative alkoxyl groups include methoxy, ethoxy, propyloxy,tert-butoxy and the like. An “ether” is two hydrocarbons covalentlylinked by an oxygen.

Analogous substitutions may be made to alkenyl and alkynyl groups toproduce, for example, aminoalkenyls, aminoalkynyls, amidoalkenyls,amidoalkynyls, iminoalkenyls, iminoalkynyls, thioalkenyls, thioalkynyls,carbonyl-substituted alkenyls or alkynyls.

The definition of each expression, e.g., alkyl, m, n, and the like, whenit occurs more than once in any structure, is intended to be independentof its definition elsewhere in the same structure.

Aliphatic is a C₁-C₁₂ chain, wherein one or more carbon atoms isoptionally substituted with a heteroatom selected from the groupconsisting of oxygen, nitrogen or sulfur. Each carbon is optionallysubstituted with a functional group selected from the group consistingof hydroxyl, thiol, amino, alkyl, alkoxy, thioalkyl, amionalkyl, aryl,aryloxy, thioaryl, arylamino, heteroaryl and cycloalkyl. Aliphatic alsoincludes optionally substituted C₁-C₁₂ alkenyl and alkynyl groups.Straight-chain or branched C₁-C₁₂-alkyl group is selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, n-butyl, 2-butyl,sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl,1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl,1-ethylpropyl, n-hexyl, 2-hexyl, 2-methylpentyl, 3-methylpentyl,4-methylpentyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl,1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl,1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethylbutyl,2-ethylbutyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-heptyl, 3-heptyl,2-ethylpentyl, 1-propylbutyl, n-octyl, 2-ethylhexyl, 2-propylheptyl,nonyl and decyl.

Cycloaliphatic is a C₃-C₇ cycloalkyl selected from the group consistingof cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. TheC₃-C₇ cycloalkyl is optionally substituted with 1, 2, 3, 4 or 5substituents selected from the group consisting of hydroxyl, thiol,amino, alkyl, alkoxy, thioalkyl, amionalkyl, aryl, aryloxy, thioaryl,arylamino, heteroaryl and cycloalkyl.

Aromatic is an aryl group selected from the group consisting of phenyl,tolyl, xylyl, mesityl, naphthyl, fluorenyl, anthracenyl, phenanthrenyl,pyridyl, and naphthacenyl, wherein the aryl group is optionallysubstituted with 1, 2, 3, 4 or 5 substituents selected from the groupconsisting of alkyl, alkoxy, thioalkyl, amino, nitro, trifluoromethyl,aryl, halo and cyano. Aromatic dialdehydes include isophthalaldehyde,phthalaldehyde and terephthalaldehyde.

Heterocycloaliphatic is a C₄-C₇ ring optionally substituted with 1, 2 or3 heteroatoms selected from the group consisting of oxygen, nitrogen andsulfur. Each carbon is optionally substituted with a functional groupselected from the group consisting of hydroxyl, thiol, amino, alkyl,alkoxy, thioalkyl, amionalkyl, aryl, aryloxy, thioaryl, arylamino,heteroaryl and cycloalkyl. Heterocycloaliphatic group includespyrrolidinyl, piperidinyl, 2,2,6,6-tetramethylpiperidinyl,imidazolidinyl, pyrazolidinyl, oxazolidinyl, morpholidinyl,thiazolidinyl, isothiazolidinyl, isoxazolidinyl, piperazinyl,tetrahydrothiophenyl, tetrahydrofuranyl, tetrahydropyranyl and dioxanyl.

Heterocyclic is a heterocycloaromatic selected from the group consistingof pyridyl, quinolinyl, acridinyl, pyridazinyl, pyrimidinyl andpyrazinyl, wherein the heterocycloaromatic is optionally substitutedwith 1, 2 or 3 substituents selected from the group consisting of alkyl,alkoxy, thioalkyl, amino, nitro, trifluoromethyl, aryl, halo and cyano.

The abbreviations Me, Et, Ph, Tf, Nf, Ts, and Ms represent methyl,ethyl, phenyl, trifluoromethanesulfonyl, nonafluorobutanesulfonyl,p-toluenesulfonyl and methanesulfonyl, respectively. A morecomprehensive list of the abbreviations utilized by organic chemists ofordinary skill in the art appears in the first issue of each volume ofthe Journal of Organic Chemistry; this list is typically presented in atable entitled Standard List of Abbreviations.

It will be understood that “substitution” or “substituted with” includesthe implicit proviso that such substitution is in accordance withpermitted valence of the substituted atom and the substituent, and thatthe substitution results in a stable compound, e.g., which does notspontaneously undergo transformation such as by rearrangement,cyclization, elimination, or other reaction.

The term “substituted” is also contemplated to include all permissiblesubstituents of organic compounds. In a broad aspect, the permissiblesubstituents include acyclic and cyclic, branched and unbranched,carbocyclic and heterocyclic, aromatic and nonaromatic substituents oforganic compounds. Illustrative substituents include, for example, thosedescribed herein above. The permissible substituents may be one or moreand the same or different for appropriate organic compounds. Forpurposes of this invention, the heteroatoms such as nitrogen may havehydrogen substituents and/or any permissible substituents of organiccompounds described herein which satisfy the valences of theheteroatoms. This invention is not intended to be limited in any mannerby the permissible substituents of organic compounds.

The term “nucleophile” is recognized in the art, and as used hereinmeans a chemical moiety having a reactive pair of electrons. Examples ofnucleophiles include uncharged compounds such as water, amines,mercaptans and alcohols, and charged moieties such as alkoxides,thiolates, carbanions, and a variety of organic and inorganic anions. Ofparticular interest herein, the free hydroxyl group on poly(vinylalcohol) are nucleophiles.

The term “electrophile” is art-recognized and refers to chemicalmoieties which can accept a pair of electrons from a nucleophile asdefined above. Electrophiles useful in the method of the presentinvention include cyclic compounds such as epoxides, aziridines,episulfides, cyclic sulfates, carbonates, hydroxysuccinimidyl esters,lactones, lactams, maleimides, and the like. Non-cyclic electrophilesinclude aldehydes, imines, ketones, phosphates, iodoacetamides,sulfates, sulfonates (e.g., tosylates), halides such as chlorides,bromides, iodides, and the like.

As used herein, the term “polymer” means a molecule, formed by thechemical union of two or more monomer or oligomer units. The chemicalunits are normally linked together by covalent linkages. The two or morecombining units in a polymer can be all the same, in which case thepolymer is referred to as a homopolymer. They can be also be differentand, thus, the polymer will be a combination of the different units.These polymers are referred to as copolymers. The relationship betweenthe polymer subunits may be oriented be head-to-head or head-to-tailrelative to each subunit.

The non-natural polymers for use in the present invention compriseeither a plurality of pendant electrophilic or nucleophilic groups.Examples of the non-natural polymers for use in the present inventioninclude, but are not limited to polyalcohols such as ethylene vinylalcohol (EVAL), hydroxyethyl acrylate, poly(ethylene glycol), poly(vinylalcohol), poly(hydroxypropyl methacrylamide), polypropylene glycol);polyamines (such as polyvinylamine, polyallylamine, tetramethyleneamine,pentamethyleneamine, hexamethyleneamine, bis(2-hydroxyethyl)amine,bis(2-aminoethyl)amine, tris(2-aminoethyl)amine, branched or linearpolyethyleneimine—e.g., Lubrasols™—and salts thereof, and derivatives ofpolyethyleneimine such as acylated polyetheyleneimine); dendrimers (suchas PAMAM Starburst dendrimers); polyalkylene glycol derivatives (such asamine-substituted polyethylene and polypropylene glycols); polyacrylates(such as amine-substituted and alcohol-substituted polyacrylates);multi-amino PEG; polymers where the backbone polymeric structure issubstituted with the following pendant nucleophilic or electrophilicgroups such as PEG substituted with amines, hydroxylamine, hydrazines,thiols, xanthates, amides, hydrazides, sulfonamides, oximes, malonates,imides, aldehydes, succinimidyl, isocyanates, vinylsulfones, oxiranes,arylhalides, allylhalides, alkyl halides, esters, ethers or anhydrides.

Therefore, as used herein “a polymer with a plurality of pendanthydroxyl groups” is a polymer, as discussed above, wherein hydroxylgroups are directly bonded to the backbone of the polymer, or areconnected to the polymer backbone via a tether, or both. An example of apolymer with a plurality of pendant hydroxyl groups is poly(vinylalcohol).

The phrase “polydispersity index” refers to the ratio of the “weightaverage molecular weight” to the “number average molecular weight” for aparticular polymer; it reflects the distribution of individual molecularweights in a polymer sample.

The phrase “weight average molecular weight” refers to a particularmeasure of the molecular weight of a polymer. The weight averagemolecular weight is calculated as follows: determine the molecularweight of a number of polymer molecules; add the squares of theseweights; and then divide by the total weight of the molecules.

The phrase “number average molecular weight” refers to a particularmeasure of the molecular weight of a polymer. The number averagemolecular weight is the common average of the molecular weights of theindividual polymer molecules. It is determined by measuring themolecular weight of n polymer molecules, summing the weights, anddividing by n.

Polyvinyl Alcohols

Polyvinyl alcohol (PVA) is a water soluble polymer which may besynthesized by hydrolysis of a polyvinyl ester, such as the acetate. PVAcan refer to a full or partial hydrolysis of a polyvinyl ester, such aspolyvinyl acetate, resulting in the replacement of some or all of theacetate groups with hydroxyl groups. For example, polyvinyl alcohol(PVA) may be produced by polymerization of vinyl acetate followed byhydrolysis of the polyvinyl acetate polymer. The degree ofpolymerization determines the molecular weight and viscosity insolution. The degree of hydrolysis (saponification) signifies the extentof conversion of the acetate moieties of polyvinyl acetate to hydroxylmoieties. For example, the degree of hydrolysis may be in the range ofabout 60 mol % to about 99.9 mol % and the MW (weight average molecularweight) may range from about 10,000 to about 250,000.

Non-Natural Polymer Subunits

As discussed throughout, one aspect of the invention relates to theformation and crosslinking of non-natural polymers comprising aplurality of a plurality of pendant nucleophilic groups (such as PVA) orelectrophilic groups. One approach to converting polymers comprising aplurality of pendant hydroxyl groups into polymers containing aplurality of pendant primary amines is to react the polymers comprisinga plurality of pendant hydroxyl groups with primary amine-containingcompounds. In certain embodiments, said primary amine-containingcompounds consist of one or more amine tethered to one or moreelectrophile, wherein said electrophile can react with a hydroxyl group.In certain embodiments, said primary amine-containing compounds areamino-aldehydes or amino-acetals. See, for example, U.S. Pat. No.2,960,384 (Osugi et al.), hereby incorporated by reference. For anotherapproach to forming amine functional derivatives of polymers with aplurality of pendant hydroxyls, see U.S. Pat. No. 6,107,401 (Dado etal.), hereby incorporated by reference, wherein cyclic amines were usedin the place of primary amine-containing compounds.

One aspect of the invention relates to a non-natural polymer or apharmaceutically acceptable salt thereof, wherein the non-naturalpolymer consists essentially of a plurality of subunits independentlyselected from the group consisting of

wherein independently for each occurrence

X is —(C(R)₂)_(n)—, —(CH₂OCH₂)_(n)CH₂—,—(CH₂)_(n)-(cycloalkyl)-(CH₂)_(n)—, or —(CH₂)_(n)-(aryl)-(CH₂)_(n)—;

R is H or lower alkyl;

Y is —NHR′, —OH, or —SH;

R′ is H, NH₂, aliphatic, aromatic, heterocyclic, cycloaliphatic orsaturated heterocyclic moiety;

n is 1-20; and about 60 mol % to about 99 mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned polymer, wherein X is —(C(R)₂)_(n)—; and R is H.

In certain embodiments, the present invention relates to theaforementioned polymer, wherein Y is NHR′; and R′ is H.

In certain embodiments, the present invention relates to theaforementioned polymer, wherein X is —(C(R)₂)_(n)—; R is H; Y is NHR′;and R′ is H.

Another aspect of the invention relates to a non-natural polymer or apharmaceutically acceptable salt thereof, wherein the non-naturalpolymer consists essentially of a plurality of subunits independentlyselected from the group consisting of

wherein independently for each occurrence

X is —(C(R)₂)_(n)—, —(CH₂OCH₂)_(n)CH₂—,—(CH₂)_(n)-(cycloalkyl)-(CH₂)_(n)—, or —(CH₂)_(n)-(aryl)-(CH₂)_(n)—;

R is H or lower alkyl;

Z is —C(O)R″, —C(S)R″, halide, —C(NR″)R″, —OP(O)(OR″)₂, —OP(O)(OR″)(R″),—OS(O)₂(OR″), or —OS(O)₂R″;

R″ is hydrogen, aliphatic, aromatic or heterocyclic;

n is 1-20; and about 60 mol % to about 99 mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein X is —(C(R)₂)_(n)—; and R isH.

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein Z is an aldehyde.

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein about 75 mol % to about 99mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein about 80 mol % to about 99mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein about 85 mol % to about 99mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein about 90 mol % to about 99mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein about 95 mol % to about 99mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein n is 1-10.

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein n is 2-8.

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein n is 3-7.

In certain embodiments, the present invention relates to theaforementioned non-natural polymer, wherein n is 4-6.

Cross-Linkers

One embodiment of the present invention relates to the cross-linking ofnon-natural polymers. It is well known in the art that bifunctional“cross-linking” reagents contain two reactive groups, thus providing ameans of covalently linking two target groups. The reactive groups ofthe “cross-linking” reagent may be either electrophilic or nucleophilic.When the non-natural polymer to be cross-linked comprises nucleophilicmoieties, the reactive groups in a chemical cross-linking reagenttypically belong to the classes of electrophilic functional groups,e.g., hydroxysuccinimidyl esters, maleimides, idoacetamides, ketones andaldehydes. However, when the non-natural polymer to be cross-linkedcomprises electrophilic moieties, the reactive groups in a chemicalcross-linker may be nucleophilic functional groups, e.g., alcohols,thiols and amines.

Crosslinkers may also be bifunctional. Bifunctional cross-linkingreagents can be divided in homobifunctional, heterobifunctional andzero-length bifunctional cross-linking reagents. In homobifunctionalcross-linking reagents, the reactive groups are identical. Inheterobifunctional cross-linking reagents, the reactive groups are notidentical. The “zero-length” cross-linking reagent forms a chemical bondbetween two groups utilizing a single functional group (e.g., a carbonylmoiety derived from carbonyl diimidazole) or without itself beingincorporated into the product. For example, a water-soluble carbodiimide(EDAC) may be used to couple carboxylic acids to amines. In addition tothe traditional bifunctional cross-linking reagents, a noncovalentinteraction between two molecules that has very slow dissociationkinetics can also function as a crosslink. For example, reactivederivatives of phospholipids can be used to link the liposomes or cellmembranes to antibodies or enzymes. Biotinylation and haptenylationreagents can also be thought of as heterobifunctional cross-linkingreagents because they comprise a chemically reactive group as well as abiotin or hapten moiety that binds with high affinity to avidin or ananti-hapten antibody, respectively.

In certain embodiments, the cross-linkers of the present invention arehomobifunctional cross-linkers. In other embodiments, the cross-linkersof the present invention are homopolyfunctional cross-linking reagents.

In certain embodiments, the cross-linkers of the present invention arepolyaldehydes. Polyaldehydes, as used herein, include compounds whichcontain two or more aldehyde moieties. In certain embodiments, thecross-linker of the invention is a dialdehyde. As will be appreciated byone skilled in the art, aldehydes described herein can exist as hydratesin aqueous solution, e.g., existing as hemi-acetals in aqueous solution.In certain embodiments, such hydrates can revert back to thecorresponding aldehyde for cross-linking. In some embodiments, hydratesof aldehydes and/or hydrates of other cross-linking activating moietiesare themselves capable of bringing about cross-linking.

In certain embodiments, the cross-linker is glutaraldehyde. It has beenfound that the absolute local concentration of glutaraldehyde must bemaintained at or below a level that does not produce undesired excessivelocal toxicity. At final concentrations of 0.75% or greater,glutaraldehyde produces significant tissue necrosis in the lung.Concentrations below this level produce limited local toxicityassociated with clinically acceptable side effects. In otherembodiments, other polyaldehydes, such as glyoxal, may be used.

In certain embodiments, the crosslinker of the present invention isrepresented by the following formula:

wherein independently for each occurrence

n is 0-12;

m is 0-12; and

Y is a di-radical of an aliphatic, cycloaliphatic, aromatic,heterocycloaliphatic or heterocyclic moiety.

In certain embodiments, the crosslinker of the invention is representedby the following formula:

where independently for each occurrence

n is 0-12;

m is 0-12; and

R₄ and R₅ are each independently hydrogen, aliphatic, cycloaliphatic,aromatic, heterocycloaliphatic or heterocyclic moiety.

In certain embodiments, the cross-linker is water soluble at aconcentration of about 0.1 mg/mL to about 5 mg/mL. In certainembodiments, the cross-linker is of biological origin. In certainembodiments, said aldehyde is an oxidized polysaccharide. In certainembodiments, the aldehyde is an oxidized polysaccharide, thepolysaccharide being at least one from the group of dextran, chitin,starch, agar, cellulose, alginic acid, glycosaminoglycans, hyaluronicacid, chondroitin sulfate and derivatives thereof. In certainembodiments, the aldehdye is dextranaldehyde. The aldehyde, especiallythe dextranaldehyde, preferably has a molecular weight of about 60,000to 600,000, in particular about 200,000. Higher molecular weights, inparticular of at least 200,000, may result in high degrees ofcrosslinking

Hydrogels

The term “hydrogels,” as used herein, refers to a network of polymerchains that are water-soluble, sometimes found as a colloidal gel inwhich water is the dispersion medium. In other words, hydrogels are two-or multi-component systems consisting of a three-dimensional network ofpolymer chains and water that fills the space between themacromolecules. As used herein, hydrogels are three dimensional networksformed by cross-linked chemical subunits which upon cross-linking trap asubstantial amount of water, such that the majority of their mass(typically greater than about 80%) is contributed by the entrappedwater.

Hydrogels suitable for use in the invention preferably crosslink uponthe addition of the crosslinker, i.e., without the need for a separateenergy source. Such systems allow good control of the crosslinkingprocess, because gelation does not occur until the mixing of the twosolutions takes place. If desired, polymer solutions may contain dyes orother means for visualizing the hydrogel. The crosslinkable solutionsalso may contain a bioactive drug or therapeutic compound that isentrapped in the resulting hydrogel, so that the hydrogel becomes a drugdelivery vehicle.

One aspect of the invention relates to a hydrogel prepared from anon-natural polymer and cross-linker; wherein said non-natural polymercomprises a plurality of pendant nucleophilic groups; and wherein saidcross-linker comprises at least two pendant electrophilic groups.

In certain embodiments, the nucleophilic groups are selected from thegroup consisting of alcohols, amines, hydrazines, cyanides and thiols.In certain embodiments, the nucleophilic groups are selected from thegroup consisting of alcohols, thiols and amines. In certain embodiments,the nucleophilic groups are amines. In certain embodiments, theelectrophilic groups are selected from the group consisting ofaziridines, episulfides, cyclic sulfates, carbonates, imines, esters,lactones, halides, epoxides, hydroxysuccinimidyl esters, maleimides,iodoacetamides, phosphates, sulfates, sulfonates, ketones and aldehydes.In certain embodiments, the electrophilic groups are aziridines,epoxides, hydroxysuccinimidyl esters, halides, sulfonates, or aldehydes.In certain embodiments, electrophilic groups are aldehydes.

Another aspect of the invention relates to the aforementioned hydrogel,where the non-natural polymer consists essentially of a plurality ofsubunits independently selected from the group consisting of

where independently for each occurrence

-   -   X is —(C(R)₂)_(n)—, —(CH₂OCH₂)_(n)CH₂—,        —(CH₂)_(n)-(cycloalkyl)-(CH₂)_(n)—, or        —(CH₂)_(n)-(aryl)-(CH₂)_(n)—;    -   R is H or lower alkyl;    -   Y is —NHR′, —OH or —SH;    -   R′ is hydrogen, NH₂, aliphatic, aromatic, heterocyclic,        cycloaliphatic or a saturated heterocyclic moiety;    -   n is 1-20; and    -   about 60 mol % to about 99 mol % of the subunits are

-   -   In certain embodiments, the present invention relates to the        aforementioned hydrogel, wherein X is —(C(R)₂)_(n)—; and R is H.    -   In certain embodiments, the present invention relates to the        aforementioned hydrogel, wherein Y is NHR′; and R′ is H.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein X is —(C(R)₂)_(n)—; R is H; Y is NHR′;and R′ is H.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein about 75 mol % to about 99 mol % of thesubunits are

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein about 80 mol % to about 99 mol % of thesubunits are

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein about 85 mol % to about 99 mol % of thesubunits are

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein about 90 mol % to about 99 mol % of thesubunits are

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein about 95 mol % to about 99 mol % of thesubunits are

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 1-10.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 2-8.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 3-7.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 4-6.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 2.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 3.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 4.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 5.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein n is 6.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the weight average molecular weight ofthe non-natural polymer is between about 10,000 and about 500,000.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the weight average molecular weight ofthe non-natural polymer is between about 50,000 and about 250,000.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the crosslinker is a polyaldehyde.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the cross-linker is a dialdehyde.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the cross-linker is glutaraldehyde.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the crosslinker is represented by thefollowing formula:

where independently for each occurrence

n is 0-12;

m is 0-12; and

Y is a di-radical of an aliphatic, cycloaliphatic, aromatic,heterocycloaliphatic or heterocyclic moiety.

In certain embodiments, the present invention relates to theaforementioned hydrogel,

wherein the crosslinker is represented by the following formula:

where independently for each occurrence

n is 0-12;

m is 0-12; and

R₄ and R₅ are each independently hydrogen, aliphatic, cycloaliphatic,aromatic, heterocycloaliphatic or heterocyclic moiety.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein said cross-linker is water soluble at aconcentration of about 0.1 mg/mL to about 5 mg/mL.

In certain embodiments, the present invention relates to theaforementioned hydrogel, further comprising an anti-infective.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein said anti-infective is tetracycline.

In certain embodiments, the present invention relates to theaforementioned hydrogel, further comprising a contrast-enhancing agent.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein said contrast-enhancing agent isselected from the group consisting of radiopaque materials, paramagneticmaterials, heavy atoms, transition metals, lanthanides, actinides, dyes,and radionuclide-containing materials.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 1minute to about 10 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 1minute to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 2minutes to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 3minutes to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 4minutes to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.0% to about 10.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.0% to about 6.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.0% to about 4.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.5% to about 3.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the nucleophile content of thenon-natural polymer is about 0.1% to about 5.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the nucleophile content of thenon-natural polymer is about 0.25% to about 4.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the nucleophile content of thenon-natural polymer is about 1.0% to about 2.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the pH is about 4.5 to about 9.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the pH is about 5 to about 7.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel is in contact with amammalian tissue.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel is in contact withmammalian pulmonary tissue.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel contacts an interiorsurface of mammalian pulmonary tissue.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel contacts an interiorsurface of mammalian alveoli.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel contacts an interiorsurface of mammalian alveoli and partially or completely fills themammalian alveoli.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel further comprises greaterthan about 90% water (w/w).

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel further comprises greaterthan about 95% water (w/w).

Another aspect of the invention relates to a hydrogel prepared from anon-natural polymer and cross-linker; wherein said non-natural polymercomprises a plurality of pendant electrophilic groups; and wherein saidcross-linker comprises at least two pendant nucleophilic groups.

In certain embodiments, the electrophilic groups are selected from thegroup consisting of aziridines, episulfides, cyclic sulfates,carbonates, imines, esters, lactones, halides, epoxides,hydroxysuccinimidyl esters, maleimides, iodoacetamides, phosphates,sulfates, sulfonates, ketones and aldehydes. In certain embodiments, theelectrophilic groups are aziridines, epoxides, hydroxysuccinimidylesters, halides, sulfonates, or aldehydes. In certain embodiments, theelectrophilic groups are aldehydes.

In certain embodiments, the nucleophilic groups are selected from thegroup consisting of alcohols, amines, hydrazines, cyanides, or thiols.In certain embodiments, the nucleophilic groups are selected from thegroup consisting of selected from the group consisting of alcohols,thiols and amines. In certain embodiments, the nucleophilic groups areamines.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the non-natural polymer consistsessentially of a plurality of subunits independently selected from thegroup consisting of

wherein independently for each occurrence

-   -   X is —(C(R)₂)_(n)—, —(CH₂OCH₂)_(n)CH₂—,        —(CH₂)_(n)-(cycloalkyl)-(CH₂)_(n)—, or        —(CH₂)_(n)-(aryl)-(CH₂)_(n)—;    -   R is H or lower alkyl;    -   Z is —C(O)R″, —C(S)R″, halide, —C(NR″)R″, —OP(O)(OR″)₂,        —OP(O)(OR″)(R″), —OS(O)₂(OR″), or —OS(O)₂R″;    -   R″ is hydrogen, aliphatic, aromatic or heterocyclic;    -   n is independently for each occurrence 1-20; and    -   about 60 mol % to about 99 mol % of the subunits are

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein X is —(C(R)₂)_(n)— and R is H.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein Z is an aldehyde.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the crosslinker is a polyamine,polyalcohol or polythiol.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the crosslinker is a diamine, dialcoholor dithiol.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the crosslinker is represented by thefollowing formula:

wherein independently for each occurrence

-   -   n is 0-12;    -   m is 0-12;    -   R₆ is selected from the group consisting of alcohols, amines,        hydrazines, cyanides and thiols; and    -   Y is a di-radical of an aliphatic, cycloaliphatic, aromatic,        heterocycloaliphatic or heterocyclic moiety.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the crosslinker is represented by thefollowing formula:

-   -   wherein independently for each occurrence    -   n is 0-12;    -   m is 0-12;    -   R₄ and R₅ are each independently hydrogen, aliphatic,        cycloaliphatic, aromatic, heterocycloaliphatic or heterocyclic        moiety; and    -   R₆ is selected from the group consisting of alcohols, amines,        hydrazines, cyanides and thiols.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the cross-linker is water soluble at aconcentration of about 0.1 mg/mL to about 5 mg/mL.

In certain embodiments, the present invention relates to theaforementioned hydrogel, further comprising an anti-infective.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the anti-infective is tetracycline.

In certain embodiments, the present invention relates to theaforementioned hydrogel, further comprising a contrast-enhancing agent.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the contrast-enhancing agent isselected from the group consisting of radiopaque materials, paramagneticmaterials, heavy atoms, transition metals, lanthanides, actinides, dyes,and radionuclide-containing materials.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 1minute to about 10 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 1minute to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 2minutes to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 3minutes to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein upon combination of the non-naturalpolymer and the crosslinker substantial cross-linking occurs in about 4minutes to about 8 minutes.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.0% to about 10.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.0% to about 6.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.0% to about 4.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the concentration of the non-naturalpolymer is about 1.5% to about 3.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the electrophile content of thenon-natural polymer is about 0.1% to about 5.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the electrophile content of thenon-natural polymer is about 0.25% to about 4.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the electrophile content of thenon-natural polymer is about 1.0% to about 2.0%.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the pH is about 4.5 to about 9.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the pH is about 5 to about 7.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel is in contact with amammalian tissue.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel is in contact withmammalian pulmonary tissue.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel contacts an interiorsurface of mammalian pulmonary tissue.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel contacts an interiorsurface of mammalian alveoli.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel contacts an interiorsurface of mammalian alveoli and partially or completely fills themammalian alveoli.

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel further comprises greaterthan about 90% water (w/w).

In certain embodiments, the present invention relates to theaforementioned hydrogel, wherein the hydrogel further comprises greaterthan about 95% water (w/w).

Ratio of Non-Natural Polymer to Cross-Linker

One aspect of the present invention relates to hydrogels prepared fromthe aforementioned components, wherein the ratio of the non-naturalpolymer to the cross-linker is greater than 5:1 (w/w). In certainembodiments, the ratio of the non-natural polymer to the cross-linker isgreater than about 10:1; about 20:1; or about 50:1 (w/w). All ratios areweight ratios; in other words, a ratio of 10:1 means the weight of thenon-natural polymer is ten times the weight of the cross-linker

Foaming

In certain embodiments, the hydrogel of the invention is administered toa patient as a foam. In other embodiments, a foam of the hydrogel of theinvention is formed within a lung of a patient.

In certain embodiments, a gas is used to form a foam of the hydrogel ofthe invention. In certain embodiments, the volume ratio of the hydrogelto the gas is about 1:1, 1:2, 1:3, 1:4, or 1:5.

In certain embodiments, the gas is non-toxic. In certain embodiments,the gas is air, helox (i.e., 79% helium and 21% oxygen), or oxygen. Incertain embodiments, the gas is oxygen.

In certain embodiments, said foam is formed outside the body viashearing of a liquid composition of the invention or a component thereofwith a gas through a plurality of syringes. In certain embodiments, saidfoam is formed outside the body via shearing of a liquid composition ofthe invention or a component thereof with a gas through two syringes. Incertain embodiments, said foam is formed inside a lung by the action ofa gas evolved from a foaming agent (e.g., a carbonate) on the liquidcomposition of the invention.

Foaming Modifiers

In certain embodiments, wherein a gas is added to the components fromwhich an aforementioned composition is formed, a foaming modifier mayalso be added. A foaming modifier is one that facilitates the generationof a stable foam. In other words, in certain embodiments a foamingmodifier may be introduced into the mixture from which a composition isformed to facilitate the formation of a foamed composition. Examples ofsuch a foaming modifier include tissue compatible surfactants,tyloxapol, poloxamers, poloxamines, phospholipids, and glycerol.Illustrative of these foaming modifiers are non-toxic surfactantsincluding, but are not limited to, fats or proteins in edible foams.However, the surfactant may be an ionic or non-ionic surfactantdepending on the intended application.

Selected Methods of the Invention

Aspects of the invention relate to hydrogel compositions that are usefulfor non-surgical lung volume reduction. According to the invention, lungvolume reduction, a procedure that reduces lung size by removing damaged(e.g., over-expanded) regions of the lung, can be accomplishednon-surgically by procedures carried out through the patient's trachea(e.g., by inserting devices and substances through a bronchoscope),rather than by procedures that disrupt the integrity of the chest wall[Ingenito et al., Am. J. Resp. Crit. Care Med. 2001, 164, 295-301;Ingenito et al., Am. J. Resp. Crit. Care Med. 2000, 161, A750; andIngenito et al., Am. J. Resp. Crit. Care Med. 2001, 163, A957.] In oneaspect of the invention relates to a method for reducing lung volume ina patient, comprising the step of administering to a patient in needthereof a therapeutically effective amount of any one of theaforementioned hydrogel compositions.

In certain embodiments of the aforementioned methods, the hydrogel isadministered using a bronchoscope. In other embodiments, the hydrogel isadministered using a catheter.

In another aspect of the invention, non-surgical lung volume reductionis performed by introducing a material (e.g., a hydrogel) into a targetregion of the lung to promote collapse of the target region. In oneembodiment, the material promotes stable collapse by adhering to thecollapsed tissue together and/or by promoting scarring of the collapsedtissue.

Suitable bronchoscopes include those manufactured by Pentax, Olympus,and Fujinon, which allow for visualization of an illuminated field. Thephysician guides the bronchoscope into the trachea and through thebronchial tree so that the open tip of the bronchoscope is positioned atthe entrance to target region (i.e., to the region of the lung that willbe reduced in volume). The bronchoscope can be guided throughprogressively narrower branches of the bronchial tree to reach varioussubsegments of either lung. For example, the bronchoscope can be guidedto a subsegment within the upper lobe of the patient's left lung.

In certain embodiments, a balloon catheter may be guided through thebronchoscope to a target region of the lung. When the catheter ispositioned within the bronchoscope, the balloon is inflated so thatmaterial passed through the catheter will be contained in regions of thelung distal to the balloon.

In certain embodiments, a method of the invention results in overalllung volume reduction of about 0.5% to about 40%. In certainembodiments, a method of the invention results in overall lung volumereduction of about 0.5% to about 30%. In certain embodiments, a methodof the invention results in overall lung volume reduction of about 0.5%to about 20%. In certain embodiments, a method of the invention resultsin overall lung volume reduction of about 0.5% to about 10%. Suchreduction may be achieved upon a single or multiple administrations ofcompositions of the present invention.

Yet another aspect of the invention relates to a method of sealing anair leak in a lung, comprising the step of administering to a lung of apatient in need thereof a therapeutically effective amount of any one ofthe aforementioned hydrogel compositions, thereby sealing the air leakin the lung.

Selected Kits of the Invention

This invention also provides kits for conveniently and effectivelyimplementing the methods of this invention. Consistent with thedefinitions in the preceding sections, such kits comprise a polymerhaving a plurality of pendant amines and a plurality of pendant hydroxylgroups, a cross-linker, and instructions for their use; and optionally ameans for facilitating their use consistent with methods of thisinvention. Such kits provide a convenient and effective means forassuring that the methods are practiced in an effective manner. Thecompliance means of such kits includes any means which facilitatespracticing a method of this invention. Such compliance means includeinstructions, packaging, and dispensing means, and combinations thereof.Kit components may be packaged for either manual or partially or whollyautomated practice of the foregoing methods. In other embodiments, thisinvention contemplates a kit including polymers and/or cross-linkers ofthe present invention, and optionally instructions for their use.

Any of these kits may contain devices used in non-surgical lung volumereduction. For example, they can also contain a catheter (e.g., asingle- or multi-lumen (e.g., dual-lumen) catheter that, optionally,includes a balloon or other device suitable for inhibiting airflowwithin the respiratory tract), tubing or other conduits for removingmaterial (e.g., solutions, including those that carry debridedepithelial cells) from the lung, a stent or a valve or other device thatmay be placed in an airway to block or reduce airflow into or out of alung or lung region, and/or a bronchoscope.

One aspect of the invention relates to a kit, comprising a firstcontainer comprising a first amount of a first mixture comprising anon-natural polymer; a second container comprising a second amount of asecond mixture comprising a cross-linker; and instructions for use inlung volume reduction therapy.

In certain embodiments, the present invention relates to theaforementioned kit, further comprising a third amount of ananti-infective.

In certain embodiments, the present invention relates to theaforementioned kit, wherein said anti-infective is tetracycline.

In certain embodiments, the present invention relates to theaforementioned kit, further comprising a fourth amount of acontrast-enhancing agent.

Therapeutic Indications

In addition to being useful for treating emphysema (e.g., as describedabove and in the following examples), hydrogel compositions of theinvention may be used in other therapeutic applications.

Another aspect of the invention may involve the use of the hydrogelcompositions to seal bronchopleural fistulas. Bronchopleural fistulasmay arise from, for example, airway leaks following surgery, lung traumaor invasive infection. The medical applications of the hydrogelcompositions can be applied to the lung of a patient to seal airwayleaks, by filling the airways and alveoli.

In certain embodiments, the present invention relates to a method ofsealing a bronchopleural fistula in a patient, comprising the step ofadministering to a patient in need thereof a therapeutically effectiveamount of any one of the aforementioned hydrogel compositions, therebysealing the fistula.

In certain embodiments, the hydrogel is administered using abronchoscope. In other embodiments, the hydrogel is administered using acatheter.

Another aspect of the invention involves the use of the inventivecompositions to achieve pleurodesis. The need for pleurodesis may arisefrom refractory medical therapy, such as malignant effusions and pleuralspace diseases. The inventive compositions can be used to fill thepleural space and thereby displace the recurrent effusions into thepleural space. In certain embodiments, the present invention relates toa method of achieving pleurodesis in a patient, comprising the step ofadministering to a patient in need thereof a therapeutically effectiveamount of any one of the aforementioned hydrogel compositions. Incertain embodiments, the hydrogel is administered using a syringe. Incertain embodiments, the hydrogel is administered using a catheter.

Another aspect of the invention involves the use of the inventivecompositions as a sealant to seal air leaks in a lung after surgery, forexample. One embodiment of the invention relates to method of sealing anair leak in a lung, comprising the step of administering to a lung of apatient in need thereof a therapeutically effective amount of any of theaforementioned hydrogel compositions, thereby sealing the air leak inthe lung.

Another aspect of the invention involves a method of attaching a firsttissue to a second tissue of a patient in need thereof comprising,applying to said first tissue or said second tissue or both an effectiveamount of the inventive compositions, thereby attaching said firsttissue to said second tissue.

Another aspect of the invention involves the use of the inventivecompositions as a general topical hemostat. The inventive compositionscan be used to control bleeding of, for example, a torn blood vessel.One embodiment of the invention relates to a method of achievinghemostasis, comprising the step of applying to a blood vessel of apatient in need thereof a therapeutically effective amount of any of theaforementioned hydrogel compositions, thereby achieving hemostasis.

Another aspect of the invention may involve the use of the hydrogelcompositions to perform emergency tamponade of bleeding vessels.Examples of bleeding vessels include, but are not limited to, majorinternal limb vessels, gastrointestinal bleeding or internal organbleeding. The inventive compositions may be used to treat bleedingvessels following trauma, surgery or gastrointestinal bleeding. Thehydrogel can be applied to permanently seal a bleeding vessel. Thehydrogel can be applied to post surgical gastrointestinal bleedingthereby sealing the vessel and preventing ongoing blood loss.

In certain embodiments, the present invention relates to a method ofadministering emergency tamponade of a bleeding vessel in a patient,comprising the step of administering to a bleeding vessel of a patient atherapeutically effective amount of any one of the aforementionedhydrogel compositions, thereby sealing the vessel.

In certain embodiments, the present invention relates to a method ofadministering emergency tamponade to a gastrointestinal vessel in apatient, comprising the step of administering to a gastrointestinalvessel of a patient a therapeutically effective amount of any one of theaforementioned hydrogel compositions, thereby sealing the vessel.

In other embodiments, the present invention relates to a method ofadministering emergency tamponade to an internal organ in a patient,comprising the step of administering to an internal organ of a patientin need thereof a therapeutically effective amount of any one of theaforementioned hydrogel compositions, thereby preventing the organ frombleeding.

Another aspect of the invention may involve the use of the hydrogelcompositions to seal fistulas. Examples of fistulas include, but are notlimited to, fistulas arising from gastrointestinal tumors and postsurgical gastrointestinal fistulas. The hydrogel compositions may beused to seal fistulas in the gastrointestinal tract arising from tumorsor surgery and thereby prevent fluid leakage into the surrounding site.The inventive compositions may be applied to permanently seal agastrointestinal fistula. In one embodiment of the invention relates toa method of sealing a fistula in a patient, comprising the step ofadministering to the gastrointestinal tract of a patient in need thereofa therapeutic amount of any one of the aforementioned hydrogelcompositions, thereby sealing the fistula.

EXEMPLIFICATION

The invention now being generally described, it will be more readilyunderstood by reference to the following examples, which are includedmerely for purposes of illustration of certain aspects and embodimentsof the present invention, and are not intended to limit the invention.

Example One Synthesis of 2% 4-Aminobutyraldehyde-FunctionalizedPolyvinyl Alcohol (2% ABA-PVA)

A 7.5% aqueous solution of polyvinyl alcohol (PVA; MW of about 100,000)was prepared by dissolving 37.5 g of PVA in 462.50 g of DI water at 90°C. The solution was allowed to cool to room temperature after the PVAhad completely dissolved. To the PVA solution was added 0.91 mL (4.66mmol) of 4-aminobutyraldehyde dimethyl acetal (ABA acetal), followed by4.46 g (45.2 mmol) of 37% aqueous hydrochloric acid. The solution wasstirred overnight, and the pH was adjusted to approximately 7 using 10 Msodium hydroxide. Approximately 6.10 g (45.8 mmol) of sodium hydroxidesolution was required for the neutralization. The solution was slowlyadded to 2 L of 99% isopropanol with vigorous stirring. The solidprecipitate was collected and dissolved in 450 mL of DI water. Theprecipitation from isopropanol was repeated two more times, and thesolid product was collected and lyophilized.

Synthesis of 4% 4-Aminobutyraldehyde-Functionalized Polyvinyl Alcohol(4% ABA-PVA)

The same procedure as for 2% ABA-PVA was followed, except 1.83 mL (9.32mmol) of ABA acetal and 4.92 g (49.9 mmol) of 37% aqueous HCl were used.

Synthesis of 6% 4-Aminobutyraldehyde-Functionalized Polyvinyl Alcohol(6% ABA-PVA)

The same procedure as for 2% ABA-PVA was followed, except 2.73 mL (13.98mmol) of ABA acetal and 5.84 g (59.2 mmol) of 37% aqueous HCl were used.

Example Two Aminated PVA/GA In Vivo Experiments in Sheep

The following procedures were used to determine the efficacy and safetyof aminated polyvinyl alcohol (aPVA) and glutaraldehyde (GA) basedtissue glues for bronchoscopic lung volume reduction (BLVR). aPVA/GAmixtures with desirable properties for BLVR were identified through aseries of in vitro experiments (described below). These formulationswere then used to perform BLVR in sheep

General Procedures

Anesthesia was induced with ketamine 2 mg/kg, midazolam 0.3 mg/kg, andpropofol 70 mg IV and maintained with propofol continuous infusion.Animals were intubated fiberoptically with a 10 mm oral endotrachealtube and mechanically ventilated with RR 12, TV 500. A baseline CT scanwas obtained at 25 cmH₂O transpulmonary pressure, measured with anesophageal balloon.

The bronchoscope was wedged in a target segmental airway. The deliverycatheter was passed through the working channel of the bronchoscopeuntil its tip was visible 1-2 cm beyond the end of the bronchoscope. TheGA solution was added to the aPVA solution. For foam treatments, foamwas generated by pushing the liquid and oxygen from a wall sourcerepeatedly through two syringes connected by a three-way stopcock. Forgel treatments, the aPVA and GA were mixed using two syringes connectedby a three-way stopcock, but no gas was added. The foam or gel was drawninto one of the syringes which was attached to the proximal end of thecatheter and injected by hand. The catheter was then removed and air wasinjected through the working channel to push the foam/gel distal. After2-3 minutes, the bronchoscope was removed from wedge position and thesite was inspected for evidence of proper polymerization of thefoam/gel. The bronchoscope was then wedged at the next target segmentwhere the procedure was repeated. Following completion of the lasttreatment, a repeat CT scan was obtained at 25 cmH₂O transpulmonarypressure. Anesthesia was discontinued and the animal was extubated andallowed to recover.

All sheep were treated with 4 days of broad-spectrum antibiotics(Baytril) beginning immediately prior to LVR. Follow-up CT scans—repeatCT scans were performed at selected timepoints prior toeuthanasia/necropsy. From 6-85 days following LVR, repeat CT scans wereperformed at 25 cmH₂O transpulmonary pressure. The animals were theneuthanized and necropsied. The abdominal and thoracic organs wereinspected. The lungs were removed enbloc and inflated and the treatmentsites were evaluated semiquantitatively. The sites were then dissectedand evaluated for evidence of hemorrhage, necrosis, or other grossevidence of toxicity. Tissue samples were taken from each lung treatmentsite as well as untreated control sites and preserved in 10% bufferedformalin for later histologic processing. Samples of heart, liver,kidney, and spleen were also collected and processed in similar fashion.

Three sheep were treated with three formulations containing a range ofaPVA concentrations from 2.025 to 2.5% and GA concentrations from 0.20to 0.25%. Sheep 343 and 385 received foam treatments in the right lungand gel treatments in the left (see FIG. 2, Table 1 and Table 2).

Results

All animals survived to planned euthanasia/necropsy. CT scansimmediately post-LVR revealed hazy infiltrates at treatment sites in allanimals (see FIG. 2, Table 3). Many of the foam-treated sites also haddenser, linear appearing areas. The foam-treated sites were generallylarger and more peripherally distributed. CT scans at one week revealedprogression towards denser, more linear infiltrates. Volume reduction of8 to 44.7 mL per site treated was detected by CT integration posttreatment and 32.9 to 63.4 mL at one week, representing 5.3 to 12.7%volume reduction.

There were no pleural adhesions in any animal. Treatment sites wereeasily identified and well localized. The foam-treated sites weregenerally larger than the gel-treated sites. The percentage of siteswith hemorrhage/necrosis ranged from 25 to 100%. For animals 343 and385, although a larger percentage of foam sites had evidence ofhemorrhage/necrosis, the actual amount of hemorrhage/necrosis at thesesites was small and unlikely to be of clinical significance.

Both the foam and gel aPVA/GA mixtures tested were effective inproducing lung volume reduction bronchoscopically.

Example Three Synthesis of Aminated PVA

Each of the experiments described below was independently completed withpolyvinyl alcohol of 150 kDa, 100 kDa, and 50 kDa.

2% 4-Aminobutyraldehyde-Functionalized PVA (2% ABA-PVA)

A 7.5% aqueous solution of polyvinyl alcohol (PVA) was prepared bydissolving 37.5 g of PVA in 462.50 g of DI water at 90° C. The solutionwas allowed to cool to room temperature after the PVA had completelydissolved. To the PVA solution was added 0.91 mL (4.66 mmol) of4-aminobutyraldehyde dimethyl acetal (ABA acetal), followed by 4.46 g(45.2 mmol) of 37% aqueous hydrochloric acid. The solution was stirredovernight. Next the pH was adjusted to approximately 7 using 10 M sodiumhydroxide. Approximately 6.10 g (45.8 mmol) of sodium hydroxide solutionwas required for the neutralization. The solution was slowly added to 2L of 99% isopropanol with vigorous stirring. The solid precipitate wascollected and dissolved in 800 mL of DI water by heating to 90° C. Whenall of the PVA is in solution, the sample was cooled to room temperatureand transferred to a 3 L carboy. The sample volume was increased toapproximately 2 L using additional DI water. The sample was purified bydiafiltration through a 10 k MW hollow fiber column, consisting of fivevolume exchanges.

4% ABA-PVA

The same procedure as for 2% ABA-PVA was followed, except 1.83 mL (9.32mmol) of ABA acetal and 4.92 g (49.9 mmol) of 37% aqueous HCl were used.

6% ABA-PVA

The same procedure as for 2% ABA-PVA was followed, except 2.73 mL (13.9mmol) of ABA acetal and 5.37 g (54.5 mmol) of 37% aqueous HCl were used.

8% ABA-PVA

The same procedure as for 2% ABA-PVA was followed, except 3.66 mL (18.6mmol) of ABA acetal and 5.84 g (59.2 mmol) of 37% aqueous HCl were used.

10% ABA-PVA

The same procedure as for 2% ABA-PVA was followed, except 4.57 mL (23.3mmol) of ABA acetal and 6.29 g (63.8 mmol) of 37% aqueous HCl were used.

The nitrogen contents of the products from the various syntheses weredetermined by elemental analysis. See FIG. 3.

Example Four Crosslinking of Aminated PVA with Glutaric Dialdehyde

In this Example, the term “buffer” refers to a 40 mmol sodium phosphatedibasic solution that has been pH adjusted from 9.2 to 8.0 using 1 Naqueous hydrochloric acid.

Glutaric dialdehyde (GDA), 50% aqueous solution, was used to make thefollowing three stock solutions: 1% GA=0.2 mL GA+9.8 mL Buffer; 2%GA=0.4 mL GA+9.6 mL Buffer; and 3% GA=0.6 mL GA+9.4 mL Buffer.

The ABA-PVA polymers were dissolved as 5% aqueous solutions, thendiluted further to 2% solutions with buffer.

The GA and ABA-PVA solutions were combined as follows: 900 uL of polymersolution+100 uL of GA solution. This combination produced solutions withthe concentrations tabulated below.

TABLE 1 Solution Concentrations ABA-PVA [%] GDA [%] Buffer [mM] 1.8 0.325.4 1.8 0.2 25.4 1.8 0.1 25.5

The experiments were carried out according to the following procedure:900 uL of polymer solution and 100 uL of GA solution were added to a 2mL Eppendorf tube and vortexed for 5 seconds. The tube was inverteduntil the solution was not flowing and represented a solid. The time tosolidification was measured. The solution concentrations yielded theresults presented in FIG. 4. The data for the 150 kDa ABA-PVA samplesshows a very distinct trend.

In this system both the amount of amination and the concentration of GAinfluence the time required to crosslink. All of the samples in this setshowed a significant difference in time required to crosslink among the0.1% GA sample and the two related samples at the same level ofamination. There is also a large difference between the 2% ABA-PVAcrosslinking time and the time required by the 4% and 6% ABA-PVAsamples, showing that the time required to crosslink is also a functionof amination.

The data for the 100 kDa ABA-PVA samples shows the same trend ofdecreasing time required to crosslink the polymer. See FIG. 5. In thisset of experiments the amount of amination appears to be the majorfactor in the time required to crosslink. The sample with the lowestpercentage of amine groups did not crosslink within 10 minutes. In the4% and 6% ABA-PVA groups, the 0.1% GA samples took 5.5 minutes and 3.75minutes, respectively, to solidify. The 0.2% and 0.3% GA samples tookapproximately one minute to crosslink.

Effect of pH on Crosslinking Times

Phosphate buffers at 40 mmol were prepared using sodium phosphatedibasic (SPD) and then adjusted to pH values between 6 and 9. The sampletested was a 150 kDa PVA with 4% ABA in the feedstock and a nitrogencontent of 0.24%. The 4% ABA-PVA polymer was dissolved as a 5% aqueoussolution, then diluted further to 2.5% solution with the variousbuffers. 900 uL of polymer solution and 100 uL of GA solution were addedto a 2 mL Eppendorf tube and vortexed for 5 seconds. The tube wasinverted until the solution was not flowing and represented a solid. Thetime to solidification was measured. The pH had a significant effect onthe time it took for the samples to crosslink. The data indicates thatthe time required to crosslink increases as the pH decreases. See FIG.6.

The 4% 150 kDa ABA-PVA sample crosslinked rapidly at the higher pHrange, between 7 and 9. At 0.2% GA concentration, crosslinking was stilloccurring at 37 seconds at pH 7. However, once the pH is adjusted to 6.5it took nearly four times as long, 2 minutes 31 seconds, to completelycrosslink. At pH 6 a sample took over 8 minutes to crosslink. Thesamples corresponding to 0.1% GA followed the same trend, albeit at amore gradual pace until pH 7. Below pH 7 the samples did not solidifywithin 10 minutes.

Example Five In-Vivo Experiments—Part I

Four animals were treated with the Polymeric Lung Volume Reduction(PLVR) system at 5-6 sites in one lung. Clinical observations, clinicalpathology, chest CT scans, and physiology were assessed immediatelypost-treatment and at 1, 4, 8, and 12 weeks. Chest CT scans andphysiology were analyzed quantitatively to assess efficacy. Clinicalobservations, clinical pathology, and qualitative CT scan findings wereused to assess safety. Animals were euthanized and necropsied at 12weeks. Tissues samples were prepared for histologic evaluation.

Test materials were formulated as two components:

aPVA: a 5% solution aPVA (1.25% amine substitution) in phosphate buffer,pH ˜6.5 was diluted in sterile water to a concentration of 2.2%. Foreach treatment site, 4.5 mL was drawn into a 20 mL syringe.

Glutaraldehyde (GA): a 25% solution of glutaraldehyde was diluted insterile water to a concentration of 2.5%. For each treatment site, 0.5mL was drawn into a 3 mL syringe.

Following final reconstitution at the time of administration, the finalconcentrations were 2% aPVA and 0.25% GA. Five mL of this solution wascombined with 15 mL of oxygen to generate 20 mL of foam for eachtreatment site. The foam crosslinked within 2-4 minutes in benchtesting.

The bronchoscope was directed into wedge position at a predeterminedpulmonary segment or subsegment. To verify that the bronchoscope was inproper wedge position, suction was applied and airway collapse distal tothe tip of the scope was visually confirmed.

A single lumen catheter (5.5 French) was inserted through the instrumentchannel of the bronchoscope until the tip of the catheter was visiblebeyond the tip of the bronchoscope. The catheter was not advanced morethan 2 cm beyond the end of the bronchoscope. If resistance wasencountered, the catheter was withdrawn 0.5 to 1 cm, ensuring that thetip of the catheter was visualized beyond the tip of the bronchoscope.

The foam was prepared for injection as follows:

The 2.5% glutaraldehyde solution (0.5 mL volume) was added to the aPVAsolution (4.5 mL volume) by injection through a 3-way stopcock in a 20mL syringe. 15 mL of 100% oxygen from a wall source was added to asecond 20 mL syringe. Foam was generated by pushing the liquid (5 mLstarting volume) and gas (15 mL starting volume) repeatedly(approximately 20 times back and forth) through the two syringesconnected by a three-way stopcock.

Injection of PLVR reagents and in situ formation of a stable foam wasperformed as follows:

The foam (containing aPVA, GA and oxygen) was drawn into one of thesyringes and then attached to the proximal end of the catheter andinjected by hand over approximately 30-40 seconds. The catheter was thenremoved and air was injected through the working channel of thebronchoscope to push the foam distal.

After 2-3 minutes, the bronchoscope was removed from wedge position andthe site was inspected for evidence of proper polymerization of thefoam. Proper polymerization was confirmed by observing no free liquid orfoam flowing back from the administration site.

CT scans immediately post treatment revealed focal infiltrates attreatment sites with evidence of volume loss at some sites. CT scans at1 week revealed dense, more linear appearing infiltrates at treatmentsites with obvious volume loss and accompanying mediastinal shift towardthe treatment side. CT scans at 8 and 12 weeks showed persistence of theinfiltrates at treatment sites with some decrease in mediastinal shift.

CT volume integration revealed peak mean volume reduction per sitetreated of 154.6 mL at week 1. By week 12, volume reduction per siteappeared to reach a plateau at 75.0 mL per site. Twelve-week changesfrom baseline in absolute R lung volume and R lung volume normalized toL lung volume were statistically significant (p<0.008 and 0.007respectively).

PLVR produced effective lung volume reduction as assessed by CT volumeintegration and physiology. (See FIG. 7) Clinical observations, clinicalpathology, CT scans, and gross and microscopic pathology revealed noevidence of pulmonary, renal, cardiac, hepatic, or hematologic toxicity.

In-Vivo Experiments—Part II

The same in-vivo experiments were performed with the test articlesbuffered with citrate buffer at pH 5.0. The polymerization time of thefoam was approximately 9 minutes in bench testing. This PLVR formulationproduced effective lung volume reduction as assessed by CT volumeintegration and physiology. The average volume reduction found by CTvolume integration was 158.7 ml/site at 1 week and 65.8 ml/site at 4weeks. Clinical observations, clinical pathology, CT scans, and grossand microscopic pathology revealed no evidence of pulmonary, renal,cardiac, hepatic, or hematologic toxicity. The lung volume reductionsachieved in-vivo with this system were comparable to the ones in Part 1.

In-Vivo Experiments—Part III

The same in-vivo experiments were performed with the test articlesbuffered with phosphate buffer at pH 6.0. The polymerization time of thefoam was approximately 2 minutes in bench testing. This PLVR formulationproduced effective lung volume reduction as assessed by CT volumeintegration and physiology. The average volume reduction found by CTvolume integration was 125.6 ml/site at 1 week and 98 ml/site at 4weeks. Clinical observations, clinical pathology, CT scans, and grossand microscopic pathology revealed no evidence of pulmonary, renal,cardiac, hepatic, or hematologic toxicity. The lung volume reductionsachieved in-vivo with this system were comparable to the ones in Part I.

In-Vivo Experiments—Part IV

The same in-vivo experiments were performed with the test articlesbuffered with phosphate buffer at pH 6.0 and instead of oxygen, air wasused to foam the liquid. The polymerization time of the foam wasapproximately 2 minutes in bench testing. This PLVR formulation producedeffective lung volume reduction as assessed by CT volume integration andphysiology. The average volume reduction found by CT volume integrationwas 182.3 ml/site at 1 week and 103.6 ml/site at 4 weeks. Clinicalobservations, clinical pathology, CT scans, and gross and microscopicpathology revealed no evidence of pulmonary, renal, cardiac, hepatic, orhematologic toxicity. The lung volume reductions achieved in-vivo withthis system were comparable to the ones in Part 1.

In-Vitro Experiments

Synthesis and Purification of aPVA

A 1 L beaker and a stir bar were rinsed with WFI and to the beaker wasadded 497.27 g of a 7.5% PVA solution (MW 85-124 kDa, 87-89% hydrolyzed)and 7.43 g of 4-aminobutyraldehyde diethyl acetal (technical grade,minimum 90%,). The beaker was covered with aluminum foil and thesolution stirred at room temperature. After one hour, 36.98 g of 10%hydrochloric acid was added to the beaker, and the solution was againcovered with foil and allowed to stir at room temperature.

After about 24 hours, 1 N sodium hydroxide was added to the solutionuntil neutral pH was reached, as indicated by pH paper and the solutionwas stirred at room temperature until homogenous. 1 liter of theaminated PVA (“aPVA”) solution was diafiltered using a 10 kDa cut-offmembrane via 9.5 exchanges with WFI. The final aPVA solution was dilutedto 2.1% with phosphate buffer, pH 6.0. The amine content of the aPVA wasdetermined by elemental analysis to be 1.43%.

By increasing or decreasing the amount of 4-aminobutyraldehyde diethylacetal, the amine content of the aPVA polymer could be controlledbetween about 0.75% and 3%. Higher (146-186 kDa, average MW 170 kDa,87-89% hydrolyzed) and lower (31-50 kDa, average MW 40 kDa, 87-89%hydrolyzed) molecular weight PVA starting materials were used to obtainaPVA utilizing the same reaction conditions.

INCORPORATION BY REFERENCE

All of the U.S. patents and U.S. published patent applications citedherein are hereby incorporated by reference.

EQUIVALENTS

While several embodiments of the present invention are described andillustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

We claim:
 1. A method of sealing a bronchopleural fistula in a patient,comprising the step of administering to a patient in need thereof atherapeutically effective amount of a hydrogel, wherein said hydrogel isprepared from a first non-natural polymer and a first cross-linker; saidfirst non-natural polymer consists essentially of a plurality ofsubunits independently selected from the group consisting of

wherein independently for each occurrence X is —(C(R)₂)_(n)—,—(CH₂OCH₂)_(n)CH₂—, —(CH₂)_(n)-(cycloalkyl)-CH_(n)—, or—(CH₂)_(n)-(aryl)-(CH₂)_(n)—; R is H or lower alkyl; Y is —NHR′, —OH or—SH; R′ is hydrogen NH₂, aliphatic, aromatic, heterocyclic,cycloaliphatic or a saturated heterocyclic moiety; n is 1-20; and about60 mol % to about 99 mol % of the subunits are

and said first cross-linker comprises at least two pendant firstelectrophilic groups, thereby sealing said bronchopleural fistula. 2.The method of claim 1, wherein said hydrogel is administered using abronchoscope.
 3. The method of claim 1, wherein said hydrogel isadministered using a catheter.
 4. A method of sealing an air leak in alung, comprising the step of administering to a lung of a patient inneed thereof a therapeutically effective amount of a hydrogel, whereinsaid hydrogel is prepared from a first non-natural polymer and a firstcross-linker; said first non-natural polymer consists essentially of aplurality of subunits independently selected from the group consistingof

wherein independently for each occurrence X is —(C(R)₂)_(n)—,—(CH₂OCH₂)_(n)CH₂—, —(CH₂)_(n)-(cycloalkyl)-CH_(n)—, or—(CH₂)_(n)-(aryl)-(CH₂)_(n)—; R is H or lower alkyl; Y is —NHR′, —OH or—SH; R′ is hydrogen, NH₂, aliphatic, aromatic, heterocyclic,cycloaliphatic or a saturated heterocyclic moiety; n is 1-20; and about60 mol % to about 99 mol % of the subunits are

and said first cross-linker comprises at least two pendant firstelectrophilic groups, thereby sealing the air leak in the lung.
 5. Themethod of claim 1, wherein X is —(C(R)₂)_(n)—; and R is H.
 6. The methodof claim 1, wherein Y is NHR′; and R′ is H.
 7. The method of claim 1,wherein X is —(C(R)₂)_(n)—; R is H; Y is NHR′; and R′ is H.
 8. Themethod of claim 1, wherein said first electrophilic groups are selectedfrom the group consisting of aziridines, episulfides, cyclic sulfates,carbonates, imines, esters, lactones, halides, epoxides,hydroxysuccinimidyl esters, maleimides, iodoacetamides, phosphates,sulfates, sulfonates, ketones and aldehydes.
 9. The method of claim 1,wherein said first cross-linker is a polyaldehyde.
 10. The method ofclaim 1, wherein said first cross-linker is a dialdehyde.
 11. The methodof claim 1, wherein said first cross-linker is glutaraldehyde.
 12. Themethod of claim 1, wherein said first cross-linker is represented by thefollowing formula:

wherein independently for each occurrence n is 0-12; m is 0-12; and Y isa di-radical of an aliphatic, cycloaliphatic, aromatic,heterocycloaliphatic or heterocyclic moiety.
 13. The method of claim 1,wherein said first cross-linker is represented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; and R₄and R₅ are each independently hydrogen, aliphatic, cycloaliphatic,aromatic, heterocycloaliphatic or heterocyclic moiety.
 14. The method ofclaim 1, wherein said hydrogel is introduced into a target region of thepatient's lung.
 15. The method of claim 4, wherein said hydrogel isadministered using a bronchoscope.
 16. The method of claim 4, whereinsaid hydrogel is administered using a catheter.
 17. The method of claim4, wherein X is —(C(R)₂)_(n)—; and R is H.
 18. The method of claim 4,wherein Y is NHR′; and R′ is H.
 19. The method of claim 4, wherein X is—(C(R)₂)_(n)—; R is H; Y is NHR′; and R′ is H.
 20. The method of claim4, wherein said first electrophilic groups are selected from the groupconsisting of aziridines, episulfides, cyclic sulfates, carbonates,imines, esters, lactones, halides, epoxides, hydroxysuccinimidyl esters,maleimides, iodoacetamides, phosphates, sulfates, sulfonates, ketonesand aldehydes.
 21. The method of claim 4, wherein said firstcross-linker is a polyaldehyde.
 22. The method of claim 4, wherein saidfirst cross-linker is a dialdehyde.
 23. The method of claim 4, whereinsaid first cross-linker is glutaraldehyde.
 24. The method of claim 4,wherein said first cross-linker is represented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; and Y isa di-radical of an aliphatic, cycloaliphatic, aromatic,heterocycloaliphatic or heterocyclic moiety.
 25. The method of claim 4,wherein said first cross-linker is represented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; and R₄and R₅ are each independently hydrogen, aliphatic, cycloaliphatic,aromatic, heterocycloaliphatic or heterocyclic moiety.
 26. The method ofclaim 4, wherein said hydrogel is introduced into a target region of thepatient's lung.
 27. A method of sealing a bronchopleural fistula in apatient, comprising the step of administering to a patient in needthereof a therapeutically effective amount of a hydrogel, wherein saidhydrogel is prepared from a second non-natural polymer and a secondcross-linker; said second non-natural polymer consists essentially of aplurality of subunits independently selected from the group consistingof

wherein independently for each occurrence X is —(C(R)₂)_(n)—,—(CH₂OCH₂)_(n)CH₂—, —(CH₂)_(n)-(cycloalkyl)-(CH₂)_(n)—, or—(CH₂)_(n)-(aryl)-(CH₂)_(n)—; R is H or lower alkyl; Z is —C(O)R″,—C(S)R″, halide, —C(NR″)R″, —OP(O)(OR″)₂, —OP(O)(OR″)(R″), —OS(O)₂(OR″),or —OS(O)₂R″; R″ is hydrogen, aliphatic, aromatic or heterocyclic; n isindependently for each occurrence 1-20; and about 60 mol % to about 99mol % of the subunits are

and said second cross-linker comprises at least two pendant secondnucleophilic groups, thereby sealing said bronchopleural fistula. 28.The method of claim 27, wherein said hydrogel is administered using abronchoscope.
 29. The method of claim 27, wherein said hydrogel isadministered using a catheter.
 30. The method of claim 27, wherein X is—(C(R)₂)_(n)—; and R is H.
 31. The method of claim 27, wherein Z is analdehyde.
 32. The method of claim 27, wherein X is —(C(R)₂)_(n)—; R isH; and Z is an aldehyde.
 33. The method of claim 27, wherein said secondnucleophilic groups are selected from the group consisting of alcohols,amines, hydrazines, cyanides, or thiols.
 34. The method of claim 27,wherein said second cross-linker is a polyamine, polyalcohol orpolythiol.
 35. The method of claim 27, wherein said second cross-linkeris a diamine, dialcohol or dithiol.
 36. The method of claim 27, whereinsaid second cross-linker is represented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; R₆ isselected from the group consisting of alcohols, amines, hydrazines,cyanides and thiols; and Y is a di-radical of an aliphatic,cycloaliphatic, aromatic, heterocycloaliphatic or heterocyclic moiety.37. The method of claim 27, wherein said second cross-linker isrepresented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; R₄ andR₅ are each independently hydrogen, aliphatic, cycloaliphatic, aromatic,heterocycloaliphatic or heterocyclic moiety; and R₆ is selected from thegroup consisting of alcohols, amines, hydrazines, cyanides and thiols.38. The method of claim 27, wherein said hydrogel is introduced into atarget region of the patient's lung.
 39. A method of sealing an air leakin a lung, comprising the step of administering to a lung of a patientin need thereof a therapeutically effective amount of a hydrogel,wherein said hydrogel is prepared from a second non-natural polymer anda second cross-linker; said second non-natural polymer consistsessentially of a plurality of subunits independently selected from thegroup consisting of

wherein independently for each occurrence X is —(C(R)₂)_(n)—,—(CH₂OCH₂)_(n)CH₂—, —(CH₂)_(n)-(cycloalkyl)-(CH₂)_(n)—, or—(CH₂)_(n)-(aryl)-(CH₂)_(n)—; R is H or lower alkyl; Z is —C(O)R″,—C(S)R″, halide, —C(NR″)R″, —OP(O)(OR″)₂, —OP(O)(OR″)(R″), —OS(O)₂(OR″),or —OS(O)₂R″; R″ is hydrogen, aliphatic, aromatic or heterocyclic; n isindependently for each occurrence 1-20; and about 60 mol % to about 99mol % of the subunits are

and said second cross-linker comprises at least two pendant secondnucleophilic groups, thereby sealing the air leak in the lung.
 40. Themethod of claim 39, wherein said hydrogel is administered using abronchoscope.
 41. The method of claim 39, wherein said hydrogel isadministered using a catheter.
 42. The method of claim 39, wherein X is—(C(R)₂)_(n)—; and R is H.
 43. The method of claim 39, wherein Z is analdehyde.
 44. The method of claim 39, wherein X is —(C(R)₂)_(n)—; R isH; and Z is an aldehyde.
 45. The method of claim 39, wherein said secondnucleophilic groups are selected from the group consisting of alcohols,amines, hydrazines, cyanides, or thiols.
 46. The method of claim 39,wherein said second cross-linker is a polyamine, polyalcohol orpolythiol.
 47. The method of claim 39, wherein said second cross-linkeris a diamine, dialcohol or dithiol.
 48. The method of claim 39, whereinsaid second cross-linker is represented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; R₆ isselected from the group consisting of alcohols, amines, hydrazines,cyanides and thiols; and Y is a di-radical of an aliphatic,cycloaliphatic, aromatic, heterocycloaliphatic or heterocyclic moiety.49. The method of claim 39, wherein said second cross-linker isrepresented by the following formula:

wherein independently for each occurrence n is 0-12; m is 0-12; R₄ andR₅ are each independently hydrogen, aliphatic, cycloaliphatic, aromatic,heterocycloaliphatic or heterocyclic moiety; and R₆ is selected from thegroup consisting of alcohols, amines, hydrazines, cyanides and thiols.50. The method of claim 39, wherein said hydrogel is introduced into atarget region of the patient's lung.